Mobile electronic devices have become ubiquitous in today's fast paced society. Various portable or mobile handheld devices can perform multiple tasks as well as provide multiple communication systems. For example, the personal digital assistant (“PDA”) cellular telephone, in addition to serving as a personal organizer and cellular phone, may also provide text messaging, paging, and Internet connectivity. Accordingly, most devices require an interface for entering alphabetic as well as numeric characters. Providing a user-friendly interface, however, can be a challenge for manufacturers because of the limited surface area available on most handheld devices.
Traditional, non-portable electronic devices including computers and other devices that reside in a wall rack or on a desktop have generally contained a terminal and an input keyboard having a layout such as a QWERTY keyboard, a keyboard that gained its name from the first six letters of the top row that spell “QWERTY”. Most users are familiar with the QWERTY layout and many mobile electronic devices have a miniaturized QWERTY keyboard. Use of keys on a miniaturized QWERTY keyboard, however, can be difficult due to reduced key size and spacing.
Other mobile devices, such as a simple cellular telephone, may include only a conventional 12-key telephone keypad, having 10 keys associated with the numeric values 0–9 and two additional keys associated with an asterisk and pound symbol. Several methods have evolved for entering text on the telephone keypad, such as for example, multi-tap or predictive text entry (e.g., T9 Text Input™ by America Online, Inc., of Dulles, Va.). Despite such methods, entering alphabetic characters via a typical 12-key telephone keypad may remain inefficient for users because the telephone keypad is not designed for text entry.